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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Dear Experts<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif""><span> </span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">I am calculating optical properties
of organic perovskite material by using quantum espresso 6.1. The calculated
optical constants are not exactly matched with available literatures. Because
in my case, the band gap energy is 3.2 eV but my absorption co-efficient graph shows
peaks in the energy region 1-3 eV too, but maximum absorption occurs in the
energy region 8-10 eV. But, If a photon having equal or greater energy than the
band gap energy would be absorbed. Now my question is why the absorption
happened below the band gap energy? Is there any offset value? Should we shift
the default energy values? <span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif""><span> </span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Thanks and Regards<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Sudha Priyanka<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Assistant Professor<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Lady Doak College<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">Madurai, Tamilnadu-625001<span></span></span></p>

<p class="MsoNormal" style="margin:0in 0in 0.0001pt;text-align:justify;line-height:115%;font-size:11pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;line-height:115%;font-family:"Times New Roman","serif"">India.<span></span></span></p>





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